Recently, in various devices, electric power is saved due to the prevalence of low-power-consumption types of devices from the viewpoint of respecting the environmental conservation and the environment-friendly performance. In the International Energy Star Program, standard values of energy consumption are defined for seven kinds of items, that are, computers, displays, printers, scanners, facsimile machines, copying machines, and multifunction peripherals (see, for example, an incorporated foundation “The Energy Conservation Center, Japan”, “Standard Values of Energy Saving under the International Energy Star Program”, [online], [retrieved on May 18, 2006], the Internet <URL: http://www.eccj.or.jp/ene-star/prog/p9.html>).
Japanese Laid-Open Patent Publication No. 2002-006696 discloses a technique which converts the value of the power consumption consumed by use of an image forming apparatus during a specific time period into the amount of CO2 discharged, obtains the amount of CO2 discharged from the consumption of the expendable supplies consumed by the use of the image forming apparatus during the specific time period, and outputs the total amount of CO2 discharged as the amount of CO2 discharged of the image forming apparatus during the specific time period.
Though the standard values for saving electric power are defined in the Energy Star Program as in the above webpage, those standard values are only to regulate the maximum electric power consumption in the low power consumption state (standby mode) by classifying the power consumption in the low power consumption state of an image forming apparatus based on the largest recoding paper sheet and the printing speed. That is, in the Energy Star Program, there are no regulations on power consumption in the operation of the image forming apparatus and supplies and replaceable portions that consumed when the image forming apparatus forms an image.
The above Japanese Laid-Open Patent Publication No. 2002-006696 describes the technique that displays the amount of CO2 discharged converted from the power consumption of the image forming apparatus. However, as to a recording sheet that is one of the supplies used when an image is formed, the amount of CO2 discharged is only displayed, that is obtained from the power consumed when the recording sheet is produced. The portion of the amount of CO2 discharged is not recognized by the ordinary users, and even when the portion is presented to the users, an improvement of the interest of the users in the ecology can not be expected.